no spark when cold

[fire810]

I have a 77 35hp evinrude electric start. I get no spark when the temperature
drops to about 50 but once the temperature rises to about 80 it starts and runs great.I have replaced the powerpack and checked all the wires.Any ideas.
Could the flywheel be shorting against the stator when cold and when heated up
by the sun it expands enough to work.

 

[ezeke]

Re: no spark when cold

Assuming that you have electric start, it is more likely that the starter is not turning the flywheel fast enough; you need to get to 250-300 RPM to get good spark. Make sure that the battery cables are in perfect shape, that all of the grounds are clean, and that your battery is fully charged.

At cold temperatures, gasoline does not vaporize readily, so more fuel is required for a cold start. The choke is there for the purpose of reducing the air intake and forcing the engine's vacuum to pull more fuel into the firing chambers. For the choke to function properly, it needs to close fully, 100%. Check it by observing the choke plate while engaging the starter and choke switch.

 

[fire810]

Re: no spark when cold

My battery and cables are fine it spins like top.The problem I have is no spark
when the weather is cool.Thanks for the advice

fire810

 

[ezeke]

Re: no spark when cold

How are you checking the spark?

 

[fire810]

Re: no spark when cold

I pull the spark plug and ground it out to the block and crank engine (coil wire is connected to it) In the morning I get no spark I try it later in the day and I can see the spark. I then replace plug in engine and it starts and runs fine. Went fishing today in the afternoon and it ran flawless . Stopped and started engine several times It is now 56 outside and it will not start (no spark)

fire810

 

[fire810]

Re: no spark when cold

Replaced the stator and it works fine now.Can not understand why the stator would not produce power when cooled down.Any ideas?

fire810

 

[Xcusme]

Re: no spark when cold

Sure, here's a SWAG.....thermal fracture of a soldered joint or wire.

When Cold:
Joint contracts, goes open circuit, no conduction, no voltage..no spark.

When Heated:
Joint expands, goes closed circuit, joint/wire conducts, viola voltage, motor starts.

Now back to your regularly scheduled programming...:redface:

 

[reload]

Re: no spark when cold

xcusme,
that is a very good explaination and may very well be correct. But in my experience as a electrical/electronic engineer it is more likely for solder joints to work in the other direction. Open when they get hot. But you are probably right.